Antioxidants in the diet and in the well-being of the pet

The free radical is defined as a molecule that contains a free electron and it is that property that makes it dangerous, since it reacts with substrate molecules, such as cellular lipids, to make the missing electron stabilize itself. Free radicals are sometimes described as pro-oxidants, in the sense that they stimulate and cause oxidation. They occur as a result of normal metabolism, but can also appear through exposure to environmental stressors such as UV radiation, pollutants, tobacco smoke, and other chemical agents.

Physiological processes in humans and animals require a constant supply of energy. This is provided in the form of energy-rich compounds (adenosine triphosphate) produced in the mitochondria of cells through the oxidation of nutrients such as glucose, fatty acids, amino acids.

Oxygen is essential for life, and without it, any cell would die in minutes. A dog at rest weighing 12kg uses approximately 4 liters of oxygen per hour. Reactions that constantly consume oxygen produce small amounts of reactive oxygen molecules (ROMs), including free radicals. A certain amount of ROM production is normal in some types of cells, such as when macrophages take over microorganisms and there is an increase in the amounts of functional anion-superoxide (O2–) and hydrogen peroxide (H2O2) radicals as 'chemical weapons' that kill bacteria and prepare them for lysosome lysis by enzymes.

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Some nutrients, such as vitamin C and vitamin E, play an important role in regulating the content of these aggressive molecules in the cell. If the levels of these nutrients fall in the phagocytes, then their bactericidal action is diminished.

There are low molecular weight compounds and endogenously produced enzymes known as antioxidants that help eliminate ROMs (see Table 1). The production of antioxidant enzymes also requires a sufficient and adequate intake of various trace minerals (Cu, Zn, Mn, Se, Fe). A catalase molecule contains 4 iron atoms. The superoxide dismutase contained in highly active phagocytes contains 2 Cu and 2 Zn atoms per molecule. Superoxide dismutase in the mitochondria contains 2 Mn atoms per molecule. Finally, there are several types of glutathione peroxidase that contain 4 Se atoms per molecule.

Table 1 - General description of the action of antioxidants on ROMs

Hence the importance of formulating food with good quality trace mineral sources that guarantee adequate levels in the body of our pets. Some antioxidants are obtained from the diet and the ingestion and absorption in sufficient quantities are important for health, since they prevent the accumulation in excess of high concentrations of ROMs in the cells and the consequent deterioration of their function; this is why it is important to achieve a balance between production and decomposition.

The presence of free radicals in the body is a constant fact. Actually, free radicals are produced during metabolic reactions. Additionally, the immune system produces free radicals as part of its normal function of destroying invading bacteria. The generation of free radicals in the body can also be induced by external environmental factors.

Free radicals are highly reactive and destroy other molecules, which in turn will form even more free radicals. The effect of this process is probably the cause of the pathogenesis of many conditions, including cancer, arthritis, cardiovascular disease, and other degenerative conditions; even the very aging process. The immune system seems to be especially susceptible to damage.

Oxidative damage and free radical formation cannot be entirely prevented. Also, once the damage has been done, it cannot be completely reversed. However, antioxidants can slow down the process a bit.

As we have been commenting on, free radicals occur regularly, so oxidative damage is a fact and what we must consider is the impact of this damage, so below I will mention some that I consider may be relevant in pets.

Cell division is a constant process in the body. An accumulation of ROMs in the nucleus of the cell leads to increased alterations (= mutations) in the structure of certain genes, causing unbridled proliferation of cells; These genes are known as oncogenes. In dogs, tumors of the skin, soft tissues (muscles, connective tissue), and the mammary gland are common. Flavonoids, ascorbic acid, and vitamin E help reduce the occurrence of genetic mutations.

The immune system is the line of defense against infections, parasitic diseases, and the development of tumors. Its function involves different types of leukocytes. The T-lymphocyte, which is produced in the thymus, recognizes pathogenic molecules; This results in an increase in the secretion of activators known as interleukins that stimulate the production of phagocytes in the bone marrow, and of lymphocytes in the lymph nodes and spleen. With age there is a decrease in the efficiency of the immune system and it is correlated to a deficient level of antioxidants.

The aging processes in the brain are caused particularly by the loss of nerve cells. Pets express it with slower reactions, decreasing learning capacity and a decrease in memory function. An adequate intake of ascorbic acid, vitamin E, flavonoids and vitamins of the B-complex are necessary to maintain the good health of this organ.

Oxidative damage and free radical formation cannot be entirely prevented. Also, once the damage has been done, it cannot be completely reversed. However, antioxidants can slow down the process a bit.

As we have been commenting on, free radicals occur regularly, so oxidative damage is a fact and what we must consider is the impact of this damage, so below I will mention some that I consider may be relevant in pets.

Cell division is a constant process in the body. An accumulation of ROMs in the nucleus of the cell leads to increased alterations (= mutations) in the structure of certain genes, causing unbridled proliferation of cells; These genes are known as oncogenes. In dogs, tumors of the skin, soft tissues (muscles, connective tissue), and the mammary gland are common. Flavonoids, ascorbic acid, and vitamin E help reduce the occurrence of genetic mutations.

The immune system is the line of defense against infections, parasitic diseases, and the development of tumors. Its function involves different types of leukocytes. The T-lymphocyte, which is produced in the thymus, recognizes pathogenic molecules; This results in an increase in the secretion of activators known as interleukins that stimulate the production of phagocytes in the bone marrow, and of lymphocytes in the lymph nodes and spleen. With age there is a decrease in the efficiency of the immune system and it is correlated to a deficient level of antioxidants.

The aging processes in the brain are caused particularly by the loss of nerve cells. Pets express it with slower reactions, decreasing learning capacity and a decrease in memory function. An adequate intake of ascorbic acid, vitamin E, flavonoids and vitamins of the B-complex are necessary to maintain the good health of this organ.

Figure 1. Mechanism of the chain reaction of lipid radicals by action of vitamin E.

The true support of antioxidants is to provide a balance that helps control the degree of oxidative damage, this is achieved by adding a variety of additional antioxidants to the diet, such as antioxidant vitamins, carotenoids or others.

Next, we will talk about some nutrients that intervene with their antioxidant action in the body of pets.

● Vitamin E

Vitamin E includes a group of chemical compounds called tocopherols and tocotrienols. Α-tocopherol is the form of vitamin E with the highest biopotency compared to the β and γ-tocopherol isomers. Vitamin E interrupts oxidation by donating electrons to free radicals that induce peroxidation of polyunsaturated fatty acids and also has important interrelationships with selenium and vitamin C. Peroxidation of body lipids can destroy the functional integrity of cell membranes , altering cell function. Vitamin E is not synthesized by the body, which is why it is considered an essential nutrient. The demand depends on the content of polyunsaturated fatty acids (PUFA) in the diet and the quality of the fats (content of peroxyl radicals). The plasma level under ideal physiological conditions should be 5 to 20 mg / l in dogs and 3 to 30 mg / l in cats.

● Vitamin C

Vitamin C is a water-soluble vitamin, essential only for some animal species that cannot synthesize it, and which, if they do not ingest it in sufficient quantity, develop the so-called "scurvy" and hence its name as ascorbic acid. Vitamin C performs numerous functions, participating in REDOX (oxidation-reduction) processes, as an antioxidant agent by itself, and also protects the antioxidant capacity of vitamin E, reacting with tocopherol free radicals. The end net result is a reduction in the amount of available vitamin C and maintenance of antioxidant levels of vitamin E.

● Minerals

Many trace minerals show at least one of their functions in the body in antioxidant enzymes. These include selenium (glutathione peroxidase); copper, zinc and manganese (superoxide dismutase); and iron (catalase). Adequate supplementation of these minerals is important for the enzymes to be synthesized by the body.

● Carotenoids

Β-carotene, lutein and lycopene are pigments that belong to the group of carotenoids and are responsible for the yellow, orange, or red colors present in many foods. Of these compounds, β-carotene is the most studied and they are not endogenously synthesized by dogs or cats. It can be a source of vitamin A since β-carotene can be transformed into this vitamin when the body needs it. However, cats cannot form vitamin A from carotenes. Carotenoids show clear biological activity as antioxidants.

Lycopene is a red pigment that occurs in tomatoes and is reported to inhibit the growth of certain types of tumors.

Lutein is produced in large quantities in green vegetables and is necessary for the elimination of ROMs in chloroplasts.

● Flavonoids

Flavonoids are yellowish-red pigments, found in vegetables and fruits (green tea and grapes); chemically they are polyphenols and help prevent arteriosclerosis and heart attacks in humans. Its main actions are to eliminate ROMs, increase the activity of glutathione peroxidases and inhibit the formation of lipid peroxyl radicals in lipoproteins.

In summary, free radicals are produced as a result of normal metabolism, but are increased under stress, exercise, or during exposure to foreign agents. Excess free radicals damage cells and can be the cause of various pathogens such as cancer, arthritis, cardiovascular diseases, even aging. A balanced nutrition of good quality trace minerals is important for the proper functioning of endogenous antioxidant systems. The inclusion of antioxidant nutrients, such as certain vitamins, carotenoids or flavonoids, helps maintain an adequate level of free radicals in the body.

Source: All Pet Food